To prospectively follow all adult patients undergoing open heart surgery for the development of post-transfusion hepatitis and by appropriate serologic tests to determine the causative agents. Primarily interested in investigating the incidence of "non-A, non-B" hepatitis and to see if there are any epidemiologic or serologic clues to its prevention. This study will also compare the clinical course of the various forms of PTH and determine the frequency with which chronic hepatitis develops.